Telescoped cylindrical ammunition has been known since the early 1970s and, compared with conventional ammunition, it has the advantage of being lighter and more compact, with the projectile being entirely received inside a cylindrical case of constant section, thereby making it possible to load a round of such ammunition axially to one end of the chamber of the gun and to extract the empty case axially through the other end of the chamber, thereby simplifying the mechanisms for extracting empty cases.
U.S. Pat. No. 4,357,857 describes an automatic gun for firing telescoped cylindrical rounds, in which a chamber disposed between the breech and the barrel of the gun is mounted to swing about an axis that is parallel to the axis of the barrel between a firing position in which the chamber is in coaxial alignment with the barrel, and a loading position in which it is angularly offset from the breech and the barrel for the purposes of receiving a new round and of enabling the empty case of the previously fired round to be ejected.
In that known gun, the recoil motion that results from firing a round is used for obtaining the angular displacement of the chamber between its firing and loading positions, and for loading a new round into the chamber and for ejecting the empty case of the previously fired round. The operation of the gun therefore depends on the operation of the rounds, and gives rise to accelerations and shocks which are considerable, and which put a severe stress on the mechanisms. In addition, in that gun, nearly all of the movements required for loading a round are performed by the chamber which is a very heavy component whose displacement consumes a large amount of energy and gives rise to violent shocks. Furthermore, a round loaded into the chamber can be fired only when the recoil portions of the gun have been returned to the battery position, thereby limiting the firing rate.